Keep or Remove Black Bars from Movies?

Question

I have been re-encoding some movies using FFMPEG. I've noticed some movies have the black bars embedded in the video stream, while others don't. Should I keep the black bars in the videos that have them and/or add black bars to the videos that don't have them, or should I use FFMPEG to crop the black bars out? I don't notice any visual difference in any video player I've tested between a film with or without the black bars, so it seems the players are able to display the video properly no matter what.

I know the reason why black bars exist (difference in aspect ratio between movie and display), but I fail to see the purpose of having them baked into the video stream. I know some movies (like the Ghostbusters reboot) use that space for visual effects, and so I wouldn't want to crop movies like that, but otherwise, wouldn't it just be a bunch of wasted storage space otherwise if I kept that padding in, or is there some technical reason why I should leave it?

Answer 1

It depends on how you intend to watch them, and whether or not the intended player is intelligent enough to recognize the blanking for titles which have them, and whether or not it will alter the aspect ratio of ones that don’t. Most players today would be fine if you removed the bars, but the best way to know for sure is to test it yourself. Videos have bars baked in when the destination format isn’t adaptive, and the viewing a/r doesn’t match the original a/r. If a player can’t detect the presence of bars, but is supplied bars, and it tries to display an a/r other than the one supplied, it will “double window” the material. Conversely, a player expecting bars, which receives the wrong material will display a cropped image.